Osteoporosis is a disease that gradually weakens bones and causes them to become brittle. Left untreated, osteoporosis can progress painlessly until a bone breaks. In some cases, osteoporosis can cause compression fractures in the spine. This occurs when the bony block, or vertebral body, in the spine collapses. This causes severe pain, deformity, and loss of height. It can also lead to nerve compression.
Until recently, doctors were limited in how they could treat osteoporosis-related spine fractures. For example, typical options included pain medications, bed rest, bracing or invasive spinal surgery. More recently, the vertebroplasty and kyphoplasty procedures have become available as therapeutic and preventive treatments for compression fractures. Vertebroplasty involves passing a bone needle slowly through the soft tissues of the back to deposit a small amount of orthopedic cement, called polymethylmethacrylate (PMMA) into the vertebral body. PMMA is a medical grade bone cement that has been used for many years in a variety of orthopaedic procedures.
Kyphoplasty is a procedure that involves making small incisions and placing a catheter into the vertebral space where the fracture is located. A cavity is created inside the bone (e.g. drilled) and a balloon, called a bone tamp, is inserted. The balloon may be support by a guidance wire that is passed through a central lumen of the catheter. The balloon is then inflated with contrast medium until it expands to a desired height, deflated and removed. The balloon is used to expand and reposition the compressed bone, and to create a cavity for cement. The cavity created by the balloon may then be filled with PMMA, binding the fracture. Kyphoplasty substantially restores height to the spine, thus reducing deformity (also pain relief).
However, the majority of the balloons utilized by kyphoplasty catheters are made of a ductile (compliant) material. Ductile materials initially undergo elastic (reversible) deformation, followed by plastic (permanent) deformation after reaching a yield point. Therefore, when the balloon is inflated in bone to reduce a fracture, it undergoes some permanent deformation (e.g., deformation of the inner tube and deformation of the balloon). As such, reinflation of the balloon will be biased. Reinserting the guidance wire would result in a non-supported distal balloon part because of the lengthening of the balloon that results from plastic deformation. Therefore, the balloon should not be reused.